Propulsion systems are used to generate thrust to achieve or maintain flight, or to control in-flight direction of vehicles, such as rockets, missiles, spacecraft, and/or aircraft. In many cases, a propulsion system may include a vessel that defines a combustion chamber in which fuel is loaded and combusted to generate high-energy combustion gas. A nozzle may be in fluid communication with the combustion chamber to receive the high-energy combustion gas and exhaust the gas out of the vessel to generate a thrust.
Conventionally, the fuel used for generating the thrust is stored external to the combustion chamber until system operation is desired. One commonly-used fuel is a monopropellant material made up of hydrazine. The monopropellant material is stored in a storage tank and is ignited by a rapid decomposition of the fuel by exposure to an iridium based catalyst. Another storable chemical propulsion system may include two hypergolic chemicals, such as monomethylhydrazine and nitrogen tetraoxide. When mixed together in a combustion chamber, the two chemicals may react to ignite and produce a hot gas (e.g., gases having a temperature greater than 1400° C.) and a desired thrust.
Although the aforementioned systems are adequate for use in many circumstances, they may be improved. In particular, some propellants may be suitable for use and/or storage on space vehicles, but they may not be useful on vehicles in which environmental considerations may be of concern, such as on naval vessels or aircraft. In other cases, monopropellants that may be considered “environmentally friendly” may have low energy density resulting in larger storage tanks that may add unwanted weight and/or may undesirably occupy space. In other cases, environmentally-friendly solid propulsion systems may not have capabilities that liquid bi- and mono-propellants provide, such as shut off capabilities and/or throttleability. Additionally, the aforementioned systems may not provide adequate thrust for propelling certain types of vehicles, and thus, uses of the systems may be limited. Moreover, although environmentally-friendly bi-propellants may have improved energy density compared to monopropellants, they may not include hypergolic chemicals. Thus, they may not be as reliable to rapidly startup and/or to operate in some altitudes as in others.
Accordingly, it is desirable to have an improved, environmentally-friendly liquid propulsion system and/or method of propelling a vehicle that may be relatively inexpensive and simple to implement. In addition, it is desirable to have a liquid propulsion system that provides improved thrust and is more lightweight than conventional environmentally-friendly liquid systems. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.